This invention relates to a continuous kneading apparatus capable of kneading a variety of material and having a small construction.
Conventionally, there have been known continuous kneading apparatus having the following construct ion. A feed section and a kneading section are formed such that material fed through a supply port into a cylinder provided with a rotatable screw shaft therein is continuously kneaded while being fed according to rotation of the screw shaft, and then extruded. Further, there has been disclosed a continuous kneading apparatus having a small construction, and yet capable of carrying out sufficient kneading. Such a continuous kneading apparatus is disclosed in, for example, Examined Japanese Patent Publication No. 2-92. In this apparatus, fixed doughnut members mounted on a cylinder and rotatable discs mounted on a rotatable shaft are alternately opposed to each other, and projected portions and recessed portions extending in radial directions are formed on opposing side faces of the rotatable discs and fixed doughnut members. With this arrangement, the shear force is applied to the material while the material is passing between the rotatable discs and fixed doughnut members.
In the latter apparatus, the material is subjected to the shear force while being fed radially outwards from center portions of the rotatable disc or being fed radially inwards from the outer portions thereof. Accordingly, the magnitude of the shear force acting on the material differs in a region close to the center portion and a region away therefrom based on a difference in the relative speed of the rotatable discs and fixed doughnut members in a circumferential direction. Thus, the material is caused to remain locally, and therefore this apparatus suffers the problem that a proper shear force cannot be applied to the entire material. More specifically, the shearing stress .tau. (kgf/cm) acting on the material can be expressed in the following equation. EQU .tau.=.eta..nu./t
where
.eta. denotes viscosity (poise); PA1 .nu. denotes shear rate (cm/s); and PA1 t denotes thickness of a shear layer.
In the above equation, the shear rate .nu. is proportion to the relative speed of the rotatable discs and fixed doughnut members. Since the thickness of the shear layer is normally fixed, the shearing stress .tau. varies in proportion to the above relative speed. Accordingly, the proper shear force cannot be applied to the entire material.